1. Technical Field
The present invention relates to a joint structure provided with a resin portion and an electrode which covers the resin portion, a piezoelectric device, a liquid ejecting head, a liquid ejecting apparatus, and a manufacturing method of the joint structure.
2. Related Art
A joint structure formed by joining two substrates is embedded in various electronic devices. For example, a liquid ejecting head mounted on a liquid ejecting apparatus such as an ink jet printer, or an ink jet plotter includes a joint structure in which one substrate on which an actuator such as a piezoelectric element is provided, and the other substrate which faces the one substrate are joined. As a joint structure which is used in the liquid ejecting head, there is a joint structure in which wiring is formed on the surface of one substrate, and the surface of the other substrate. In addition, wiring in the one substrate and wiring in the other substrate are connected through a bump electrode.
Here, as the above described bump electrode, there is a bump electrode including a series of resin layers formed on a substrate, and an electrode (wiring) formed on the surface of the resin layer (for example, JP-A-2009-260389). In addition, in a portion in the resin layer corresponding to a portion between electrodes adjacent to each other (that is, between bump electrodes), a part of the surface is shaved using etching, and becomes small. That is, a height of the resin layer between adjacent electrodes (dimension from substrate to top face of resin layer) is formed to be lower than a height of a resin layer located just below the electrode (in short, resin layer in portion covered with electrode) (refer to JP-A-2009-260389).
However, in the above described configuration, there is a concern that residue may remain on the substrate when etching the resin layer between electrodes. This point will be described in detail with reference to a configuration of a bump electrode 91 in the related art illustrated in FIG. 28. As illustrated in FIG. 28, the bump electrode 91 in the related art is provided with a resin portion 92 which protrudes onto a substrate 90, and an electrode 93 stacked on the surface of the resin portion. It is possible to configure such an electrode 93 using the same material as that of wiring 94 on the substrate 90. For example, it is possible to set the wiring 94 on the substrate 90 to the electrode 93 by extending the wiring to a portion which overlaps with the resin. In addition, as illustrated in FIG. 28, a plurality of the electrodes 93 are disposed on the resin portion 92 with intervals. A height of the resin portion 92 from the surface of the substrate 90 between the electrodes 93 is set to be lower than a height of the resin portion 92 from the surface of the substrate 90 which is located just below the electrode 93. In addition, as a forming method of such a resin portion 92, a method of removing a part of the resin portion 92 between the electrodes 93 using etching (specifically, dry etching) the resin portion 92 using the electrode 93 as a mask is adopted. However, when forming the resin portion 92 using such a method, there has been a concern that residue 95 may remain in a region in which the resin portion 92 is removed from the surface of the substrate 90. That is, there has been a concern that the residue 95 may remain on the substrate 90 between the electrodes 93. When the residue 95 remains, a short circuit between the electrodes 93 due to migration easily occurs. As a result, there has been a concern that reliability of a joint structure with such a structure may decrease.